Fit Testing

3M Center for Respiratory Protection

Overview of the Fit Testing Process

Tight-fitting respirators must seal to the wearer’s face in order to provide expected protection. This includes disposable respirators (also called “filtering facepieces”). Therefore, fit testing is required in many countries before a user wears a mandatory respirator on the job. In addition, fit tests should be performed:

Whenever a different size, style, model or make of respirator is used.

When any facial changes occur that could affect fit, such as significant weight fluctuation or dental work.

On a frequent basis in some countries, for example in the US fit testing must be repeated at least annually

Current fit testing regulations don’t require fit test administrators (fit testers) to be certified, but they must be competent to conduct a test, coach wearers to fit respirators correctly, recognize invalid tests, and properly clean and maintain equipment. However, some countries have voluntary fit tester competency assessment schemes, for example the BSiF Fit2Fit scheme which operates in the UK.

Qualitative Fit Test (QLFT)

A qualitative fit test (QLFT) may only be used to fit-test:

Filtering facepieces and half-masks (with particulate or combination filters) only. Qualitative methods may be suitable for full face masks according to some fit test regulations and only in certain circumstances. QLFT is pass/fail and relies on the user’s senses to taste an approved test agents, the predominant agents being:

o Saccharin (sweet taste); can test respirators with a particulate filter of any class.
o Bitrex® (bitter taste); can also test respirators with particulate filters of any class.

Quantitative Fit Test (QNFT)

A quantitative fit test (QNFT) can be used to fit-test any tight-fitting respirator. It involves using an instrument to measure leakage around the face seal and produces a numerical result called a “fit factor.” There are three commonly-accepted QNFT test protocols:
o Generated aerosol uses a non-hazardous aerosol such as common salt (NaCl) generated in a test chamber.
o Condensation nuclei counter (CNC) uses ambient aerosol and doesn’t require a test chamber.
o Controlled negative pressure (CNP) uses a test that creates a vacuum by temporarily cutting off air. (There is also a fourth method, which is an abbreviated version of this one.)

QNFTs use the same seven exercises as QLFTs (in the US plus an additional “grimace” test where the subject smiles or frowns for 15 seconds).

A fit factor of at least 100 is required for half-mask respirators and a minimum fit factor of 500 (US) or 2,000 (UK) for a full facepiece negative-pressure respirator.

The Importance of Fit

Respirator fit is important because it involves several major issues:

Seal.

Compatibility.

Stability.

The Respirator's Seal

A good fit means the respirator will seal to your skin. A respirator can only work when air passes through the filter. Air will take the path of least resistance, so if the seal isn’t there, the air will go around rather than through the respirator – and therefore lessen the protection.

Respirator Stability

The better a respirator fits, the more stable it’s likely to be on the wearer’s face. Fit testing determines the respirator’s ability to retain its seal when the worker is in motion. That’s why test subjects are told to go through several exercises as part of testing. A respirator that shifts during movement may not be able to retain its seal.

Compatibility with other PPE

Safety glasses, hearing protection, face shields, hard hats and coveralls can all vie with a respirator for real estate on a person’s face, head or body. For instance, if a half face respirator doesn’t fit well (especially if it’s too large), it can overlap with glasses. The more that happens, the more fogging can potentially occur on glasses, and the more likely it is that they’ll interfere with the respirator’s seal.
See the product User Instructions for more details.

To catch these problems before they happen on the job, fit test regulations require any PPE that could interfere with the respirator’s seal to be worn during the fit test.

User Seal Check: An Essential Everyday Test

Employees wearing tight-fitting respiratory protection should perform a seal check each time they put on their respirator, and may be required to do so by national regulations unless the use of the respirator is voluntary. A fit test ensures that the respirator is able to fit and provide a secure seal, but a user seal check ensures that it’s being worn right each time.

Users can either perform a positive-pressure or negative-pressure seal check:
o A positive-pressure check means blocking the exhalation valve on a half or full facepiece respirator or covering the respirator surface on a filtering facepiece, usually by using your hands, and trying to breathe out. If slight pressure builds up, that means air isn’t leaking around the edges of the respirator.
o A negative-pressure check involves blocking the intake valves on a half or full facepiece respirator or covering the respirator surface on a filtering facepiece, typically using your hands and trying to breathe in. If no air enters, the seal is tight.

See the product User Instructions for more details.

Fast Facts About Fit Testing

Fit testing is not only required by many national regulators; it’s vital to respiratory safety. This list provides some of the whys and hows of fit testing.

In addition, fit testing of employees must occur whenever a different size, style, model or make of respirator is used; when any physical change occurs that could affect fit (such as, for example, significant weight fluctuation, dental work, or other facial changes);and according to some national regulators on a regular basis, for example in the US OSHA stipulates at least annually.

However, the many national regulations do specify that fit test administrators (fit testers) should know how to conduct a test, recognize invalid results, and properly clean and maintain equipment. Some countries have voluntary fit tester competency assessment schemes, for example the BSiF Fit2Fit scheme which operates in the UK (link to www.fit2fit.org)

A qualitative fit test (QLFT) may only be used to fit-test certain negative-pressure, air-purifying respirators and tight-fitting positive-pressure, atmosphere-supplying respirators. It relies on the user’s ability to detect a particular taste, smell or irritant. A quantitative fit test (QNFT) can be used to fit-test any tight-fitting respirator. It involves using an instrument to measure leakage around the face seal and produces a numerical result called a “fit factor.”

Without fit testing, there’s no way of knowing if the respirator is actually able to provide its advertised level of protection for a specific worker. A poorly fitting respirator will likely not provide the stated nominal protection factor (NPF) or assigned protection factor (APF) level of protection to the worker and they may be exposed to the workplace respiratory hazard.

A respirator can only work when air passes through the filter. Air will take the path of least resistance, so if the seal to the face isn’t secure, the air will go around rather than through the respirator. Therefore, it is essential to ensure a proper fit when wearing tight-fitting respirators.

Respiratory protection is often worn simultaneously with other personal protective equipment (PPE). Safety glasses, hearing protection, face shields, hard hats and coveralls can all vie with a respirator for real estate on a person’s face, head or body, and could interfere with the respirator’s seal. Fit testing should ensure that equipment is compatible and doesn’t reduce the effectiveness of the respirator due to a compromised face seal.

Beards, mustaches, or even stubble interfere with the seal of a tight-fitting respirator. That’s why regulators require that employees be clean-shaven the day of the fit test and prohibits any facial hair in areas where the respirator comes into contact with the face.

That’s why fit testing involves several exercises, such as head turning and speaking. This determines the respirator’s ability to retain its seal when the worker is in motion.

Fit Testing Resources

Fitting Posters - 3M™ Disposable Respirators

As pioneers in the field of respiratory protection, we not only invented the first NIOSH approved filtering facepiece disposable respirator, we helped develop qualitative fit testing protocol used today. We have a deep bench of experienced and passionate experts eager to spread knowledge about and increase understanding of this crucial part of respiratory protection.

Fit Test Record

The Fit Testing Record is the employer documentation that fit testing has been completed and passed for employees. This record must be kept with the respiratory protection program documentation until the next required fit testing.